Researchers from Tel Aviv University believes that the war between the sexes begins in the womb. Also, a brother twin can compromise the health of his twin sister even before she is born.

The study, recently published in the journal "Pediatrics" was
led by Prof. Brian Reichman, a lecturer in pediatrics at Tel Aviv University's Sackler School of Medicine. This new study is expected to help pediatricians better understand the health risks and outcome of premature babies.

Researchers conducted the study by analyzing the information collected by Israel Neonatal Network comprising 8,858 very low birth weight infants (1 to 3 pounds) born prematurely at 24 to 34 weeks' gestation born between 1995 and 2003. The data included premature newborn singletons, same-sex and mixed-sex twins.

When both premature twin boys and premature twin girls were compared, the premature twin girls displayed 60% advantage. Also, the premature twin girls tended not to develop respiratory distress syndrome and chronic lung diseases many times found in premature boys, but this advantage seems to have been lost in infant girls with a brother twin.

Brian Reichman said, "The male disadvantage, the study suggests, seems to be transferred from the boy to the girl in utero,"

The twin studies normally concentrates on what happens after the birth when they are exposed to complex environmental and behavioral factors.

On the contrary, Reichman says, "The effects are occurring already in the uterus."

Dr. David K. Stevenson, from Stanford University, sums up the findings by saying that; "For the time being, there remains some biological truth to the old nursery rhyme that boys are made of snakes, snails and puppy dogs' tails, and girls are made of sugar and spice and everything nice. Perhaps nature knows something we do not."